A block just begins to slide over a horizontal floor, when pulled by a force of $10 \mathrm{N}$. If we pull it by a force of  $6 \mathrm{N}$, the force of friction that will come in to play is :

A cubical block of mass $m$ is held stationary against a rough wall by applying a horizontal force $F$, as shown. Which of the following statements is incorrect?

In the figure, a ladder of mass $m$  is shown leaning against a wall. It is in static equilibrium making an angle $\mathrm{\theta }$ with the horizontal floor. The coefficient of friction between the wall and the ladder is ${\mu }_1$ and that between the floor and the ladder is ${\mu }_2$. The normal reaction of the wall on the ladder is $N_1$ and that of the floor is $N_2$. If the ladder is about to slip, then: